A bandgap circuit is a circuit which provides a fixed voltage or current, regardless of power supply variations and temperature changes. Typically, bandgap circuits are composed of bipolar junction transistors (BJTs), which are not generally suitable for small, low cost, integrated circuits. There have been attempts at designing metal-oxide-semiconductor field-effect-transistor (MOSFET) based bandgap circuits, however the temperature variations of MOSFETs are far more complex than those of BJTs and it is difficult to trim. Additionally, as with prior art BJT based bandgap circuits, only one of a fixed current and a fixed voltage are provided, thereby requiring a very precise and temperature-invariant resistor to provide a fixed voltage/current ratio.
What is desired, and not provided by the prior art, is a circuit which can utilize FET technology and that provides a fixed voltage/current ratio.